Bulk- and surface-state two-electron photoemission from Cu(111)

We study theoretically the one-photon two-electron emission from the Cu(111) surface. Tuning the energy to either the surface state or to the d-band energy regions this sample provides a paradigm example of the two-particle emission from a (quasi) two-dimensional and a three-dimensional system, respectively. The independent electron-gas behavior of the surface-state electrons results in a characteristic angular pattern. We inspect the dependence of this angular shape on the strength of the electron-electron interaction. Furthermore, it is shown that the two-particle energy correlation behaves differently for bulk and surface states. (c) 2007 Elsevier B.V. All rights reserved.